X-Message-Number: 5034
From:  (Thomas Donaldson)
Subject: cryonet.message.re.biopsies
Date: Sat, 21 Oct 1995 16:41:49 -0700 (PDT)

Hi again!

Mike Darwin, in discussing the possibility of taking brain samples, also
expanded on what he really wants quite a lot. Biopsies of brain tissue are
ordinarily very small. They are also done with some care to avoid taking
tissues which might be important and to avoid hitting the patient's 
circulatory system with the needle.

When this idea was originally told to me, it sounded as if Mike wanted large
chunks. This did not look like a good idea at all and still doesn't. A
biopsy, however, might well turn out to be very useful. It would still have
to be done carefully, depending on when it was done. If done before 
perfusion, we'd have to worry about striking a blood vessel... for the same
reasons (you don't want your perfusion solution to accumulate in one 
particular part of the brain because of the leak). If done after perfusion 
is complete, just before cooldown, this problem should vanish. Again, some
brain areas are likely to be more critical than others. I would strongly
suggest that when possible the biopsy should be taken, say, from motor
areas in the cortex. Since we can't get at the hippocampus without 
going through a lot of other brain, (perhaps with neuropatients that could
be avoided, in which case I would put the hippocampus over ANY cortex 
tissue) it's probably not the area to choose. Finally, of course, I would
NEVER suggest taking lots of tissue with lots of different biopsies.

I will also point out that biopsies aren't simple to do in living patients.
The head is clasped quite firmly so that the needle doesn't move to any
other area and so cause more damage. I would suggest that a similar 
apparatus be used in biopsying suspenson patients.

Mike gives one big reason why he does not think a biopsy would matter.
That is that the patients have already sustained lots of damage. Particularly
when we talk about cryonics I think that is fallacious. Though we are coming
to understand it, as yet we don't even have a fully verified theory of how
memories are stored. Not only that, but we almost know a priori that a 
great deal of cellular machinery could be damaged WITHOUT affecting storage
of memory. It is far too facile to believe that our current limits of 
repair may not extend much farther at some future time. Much of the damage
will certainly make the patient's cells "not viable" with current techniques,
but for storage of memory alone we don't necessarily even need "viable" cells.

What these observations suggest to ME is that we should take some care in
choosing the brain area from which we take the biopsy. The more tissue, the
more care ...REGARDLESS of the condition of the patient. A simple biopsy
needle, though, when used only once, and with precautions to hold the head
firmly in place while it's done, will almost certainly not do any significant
damage. In that sense I withdraw my objection.

			Best and long long life,

				Thomas Donaldson


Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5034